Elements of electricity, magnetism, and electro-magnetism : embracing the late discoveries and improvements : digested into the form of a treatise, being the second part of a course of natural philosophy : compiled for the use of the students of the University at Cambridge, New England / by John Farrar.

John Farrar

Date:: 1826

Credit: Elements of electricity, magnetism, and electro-magnetism : embracing the late discoveries and improvements : digested into the form of a treatise, being the second part of a course of natural philosophy : compiled for the use of the students of the University at Cambridge, New England / by John Farrar. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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$When such a condenser communicates with an electrical machine by one of its metallic faces, the other communicat- ing with the ground, the latter is in the same state, as if it had been brought, without a discharge, very near to a highly charg- ed conductor. The union of these circumstances is therefore extremely well adapted to produce a strong discharge. Thus when we take in one hand the foot of the condenser, which makes us partake of its electrical state, and with the other touch the collector plate, the accumulated electricities are discharg- ed, and unite with much force through the medium of the body. This discharge produces a shock in all the organs, which is the more violent according ^- the condenser is larger, its charge stronger, and its plates nearer together. This shock transmits itself through several persons holding each other by the hand, but becomes gradually weaker as it proceeds, and this diminution of force is owing doubtless to the resistance which the bodies in question, not being perfect conductors, oppose to the passage of the electric fluid. 73. The whole force of condensers may be calculated up- on the following principle, which indicates at the same time the the manner and the limits of the accumulation which they pro- duce. The electricity Jl being introduced into the collector plate, neutralizes at a distance a portion — B, of the contrary electricity, upon the lower plate which communicates with the ground, and prevents it from escaping. This in its turn fixes, in the same way, a portion £' of the electricity of the collector plate and takes from it its expansive force. The collector plate is therefore in exactly the same situation as if it had on]y A — A' of free electricity; consequently it must continue to be charged until this quantity equals that which it would have taken imme- diately from the conductors with which it communicates, if it had been placed alone in contact with them, without the influ- ence of the lower plate. The ratio of ^ to — B and of— 5 to A' depends on the greater or less distance between the plates. But, in all cases, — B must be weaker than A, independently of the sign, so that if .^ is vitreous and B resinous, these two quan- tities united, will become vitreous. For the attractions of the particles -\- A upon — B must be less at a distance than it would be in contact; since, therefore, they neutralize — B and take$

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